<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>塌陷问题</title>
    <style>
       .father{
        width: 300px;
        height: 300px;
        background-color: pink;
        /* padding-top: 70px;
        /* 添加这个让盒子不被撑大 */
       /* box-sizing: border-box; */
       /* 溢出隐藏了 */
       /* overflow: hidden; */
       /*border-top: 1px solid black;*/
       }
       .son{
        width: 100px;
        height: 100px;
        background-color: orange;
        margin-top: 50px;
       }
    </style>
</head>
<body>
    <div class="father">
        <div class="son">son</div>
    </div>
</body>
</html>
